Jet engine combustion system having burner in the jet pipe and controlling means therefor



y 1954 o. N. LAWRENCE 83,349

JET ENGINE COMBUSTION SYSTEM HAVING BURNER IN THE JET PIPE ANDCONTROLLING MEANS THEREFOR Filed Oct, 27, 1950 W zZl/UelbtOl Fig.2

Patented July 13, 1954 TENT OFFICE JET ENGINE COMBUSTION SYSTEM HAVINGBURNER IN THE JET PIPE AND CONTROL- LING MEANS THEREFOR Owen NapierLawrence, Dorridge, England, as-

signor to Joseph Lucas Limited, Birmingham,

England Application October 27, 1950, Serial No. 192,411

Claims priority, application Great Britain November 17, 1949 3 Claims.

This invention relates to the combustion systems of jet engines, of thekind in which the system (or each of an associated group of suchsystems) comprises an elongated combustion chamber which at one end isprovided with a liquid fuel burner and is adapted for the admissionthereto of air from a blower, the other end terminating in an extensionwhich forms the jet pipe, and in which there is mounted, between theadjacent ends of the combustion chamber and jet pipe, the rotor of aturbine which actuates the blower.

In some such systems provision is made for admitting additional liquidfuel to a. burner in the jet pipe, when it is required to augment theenergy of the gases therein after passing the turbine and beforedischarge to the atmosphere. It is undesirable however, to admit theadditional fuel at an excessive rate. The permissible maximum rate ofsupply is not a fixed quantity, but is dependent on contemporary workingconditions in the system, and the object of the present invention is toenable the rate of supply to be automatically controlled in asatisfactory manner.

The invention comprises the combination with the system, of means forcontrolling the additional fuel under the joint action of the pressureof the air at the blower inlet, and the pressure of the gas in the jetpipe between the turbine and the point of admission of the additionalfuel.

The invention also comprises means as specified in the precedingparagraph, in which the relative effects of the said pressures isvariable unde manual control.

In the accompanying drawing, Figures 1 and 2 are diagrams illustratingtwo embodiments of the invention.

Referring to Figure 1, the principal combustion chamber of a jet-engineis represented by a. In this is mounted a liquid fuel burner b which issupplied by a pump at a variable rate in response to the control of thepilot and. of conditions associated with the working of th engine, suchas speed, 01' atmospheric pressure. The blower for air required in thecombustion chamber is represented by c and this is driven by a turbine11 situated at the discharge end of the combustion chamber. In theextension or jetpipe e of the combustion chamber is arranged a burner fby which the additional fuel is supplied, and it is the control of thisfuel which forms the subject of the present invention.

In the example illustrated 'at Figure l, the extra fuel is supplied by arotary pump 5/ of the swash plate type, the output of the pump beingvariable by adjustment of the obliquity of the swash plate h under theaction of a fuel-operated servo-mechanism. This mechanism is of knownform and comprises a cylindrical chamber 2' containing a piston 7'loaded by a spring k and connected to the swash plate by a rod m. Oneend of the cylinder 2' is in communication with the discharge passage nof the pump by way of a passage 0, and the other end is in communicationwith the passage 11 by way of a restricted passage 21. The end of thecylinder 11 containing the spring communicates with the seating q of acontrol valve 1" by way of a passage (1;. The arrangement is such thatwhen the valve 1" is closed, the liquid pressures acting on oppositesides of the piston are balanced, and the spring is then moves thepiston in the direction for increasing the pump output. When the valve 7is opened, a preponderating liquid pressure acts on the side of thepiston in opposition to the spring and moves the piston in the directionfor reducing the pump output.

The valve 1' is mounted on a lever s which is carried by a flexiblediaphragm t, or is pivotally mounted on a partition, which separates twocompartments in, 'u, in a chambered body part, the compartment it beingin communication with the pump inlet, or a sump. The end of the leverwhich extends into the compartment 1) is connected by a link 2 to adiaphragm 3. One side of the diaphragm is subject to the pressure of theair at the inlet side of the blower c, a passage 4 being providedbetween the blower inlet and the compartment 12. The other side of thediaphragm is subject to the pressure of the gases at the exit side ofthe turbine at, a passage 5 being provided for effecting communicationbetween the said side of the turbine and diaphragm.

In the chamber 1) is also contained another lever 6 loaded by a spring 1and evacuated capsule 8. Between the two levers s, 5 is arranged aslidable abutment 9 by which force can be transmitted from one lever tothe other, and the position of the abutment relatively to the lever ismovable under the manual control of the pilot through a lever iii. Byappropriately adjusting the position of the abutment 9 the forces actingon the valve lever 1' can be varied as desired.

Assuming that the pressures acting on the diaphragm 3 and capsule 8 aresuch that the valve 1' is slightly open, and that the piston j is inequilibrium at a position intermediate the ends of the chamber 2', itwill be seen that the pressure exerted on the left hand side of thepiston by liquid admitted to the corresponding end of the chamberthrough the passage 0 is balanced by the pressure exerted on the otherside of the piston by the combined effect of the spring k: and theliquid admitted to the right hand end of the chamber through therestricted passage p, the liquid pressure in the last mentioned end ofthe chamber being partially relieved by leakage of liquid past the valver. If now the valve r is opened to a greater extent by relativevariation of the pressures acting on the diaphragm it and capsule 3, theliquid pressure in the right hand end of the chamber 2' will be furtherrelieved, and the piston will be moved against the action of the springis by the preponderating liquid pressure in the left hand end of thechamber to cause reduction of the pump output until a new condition ofequilibrium is reached. Closing movement of the valve 1' by relativevariation of the pressures acting on the diaphragm 3 and capsule 8 has areverse effect to that above described, and enables the spring is tomove the piston 7 for increasing the pump output. Movement of theabutment a under the control of the pilot varies the efiect of thecapsule 8 on the lever s without varying the effect of the diaphragm 3on this lever.

It will be apparent therefore, that by the arrangement above described,the rate of supply of fuel from the pump g to the burner f isautomatically controllable by the pressures acting on the diaphragm 3,the air pressure acting on the capsule 8 and the load exerted by thespring 7, the effect on the valve 1" being variable under the control ofthe pilot through the lever it and abutment 9.

The embodiment shown in Figure 2 differs from that shown in Figure 1, inthat the one pump g supplies liquid fuel to both of the burners b, f. Inthis example the servo-mechanism i, 7, 7c, 0, go above described servesmainly to control the supply of fuel to the burner 19, and this iseffected in response to any control device positioned as indicated by 13in the diagram between the servomechanism and the burner b. The supplyof fuel from the pump to the burner f is mainly controlled by a throttleH, which is actuated by a second servo-mechanism indicated genericallyby i2 and which. is essentially similar to the one above described withreference to Figure 1. The servo-mechanism 22 is controlled by a similarvalve mechanism to that already described, similar reference charactersbeing used in Figure 2 to identify the. valve mechanism.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. A jet-engine combustion system having in combination anelongatedcombustion chamber, a main burner in the combustion chamber, a blowerfor supplying air under pressure to one end of the combustion chamber, aturbine at the other end of the combustion chamber, a jet pipe extendingfrom the last mentioned end of the combustion chamber, an auxiliaryburner in the jet pipe, means for supplying liquid fuel to the auxiliaryburner, a liquid-operated servo-mechanism for determining the quantityof liquid fuel supplied to the auxiliary burner, control meansresponsive to'theairpressure at the blower inlet,

additional control means responsive to the gas pressure in the jet pipebetween the turbine and the auxiliary burner, and a control memberresponsive-to the combined action of the two control means forcontrolling the action of said servomechanism.

2. A jet-engine cmbustion system as claimed in claim 1 and havingmanually adjustable means for varying the combined effect of said twocontrol means on said control member, said manually adjustable meansbeing formed in part by a motion-transmitting abutment through which oneof said two control means acts on said control member.

3. A jet-engine combustion system as claimed in claim 1, in which themeans for supplying liquid fuel to said auxiliary burner comprises apump which serves also for supplying fuel to main burner, and in which athrottle operable by the liquid-operated servo-mechanism is provided forcontrolling the quantity of liquid fuel supplied to said auxiliaryburner.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,438,663 Greenland Mar. 30, 1948 2,498,939 Bobier, Jr. Feb.23, 1950 2,503,048 Ifield Apr. 4, 1950 2,506,611 Neal et al May 9, 19502,537,772 Lundquist et a1. Jan. 9, 1951 2,545,703 Orr, Jr Mar. 20, 19512,566,373 Bedding Sept. 4, 1951 2,580,962 Sdille Jan. 1, i952 FOREIGNPATENTS Number Country Date 578,311 Great Britain June 1946

